Methods and systems are disclosed for estimating a glucose level of a person having diabetes comprises. One method may comprise: receiving into a computing device a plurality of measured glucose results from a glucose sensor coupled to the person; using the computing device to analyze the plurality of measured glucose results with a probability analysis tool configured to determine a probability of glucose sensor accuracy based on the plurality of measured glucose results; and using the computing device to estimate a glucose level of the person with a recursive filter configured to estimate the glucose level based on the plurality of measured glucose results weighted with the probability of glucose sensor accuracy.